Process of preparing fresh green vegetables



Patented Mar. 1c, 1948 I i v 2,437,859

UNHED STATES PATENT OFFICE PROCESS OF PREPARING FRESH GREEN VEGETABLES Orville Lee Moulthrop, Selma, CaliL, assignor to Western Frozen Foods 00., Fresno, CaliL, a corporation of California No Drawing. Application June 25, 1945, Serial No. 601,544

6 Claims. (01. 99-154) 1 2 This invention pertains to an improved process Brussels sprouts, broccoli, peas, asparagus, of preparing fresh green vegetables for canning spinach. vined lima beans. etc. and freezing, so that such vegetables may be The process may be carried out in various packaged, quickly frozen and then maintained forms of apparatus but the use of a long conin a state which allows them to be shipped and E veyor belt made from wire netting or other stored for appreciable periods of time before they foraminous material, such as wire mesh, has been areused. v found extremely satisfactory. Such conveyor The quick freezing of vegetables is well known. belt may move at a predetermined speed and a One of the disturbing factors'which have limited series of different operations may be carried out the use and sale of frozen vegetables is the fact 1 upon the vegetables supported and moved by the that upon thawing, the vegetables lack the conveyor. In the performance of the process. brilliance and sparkle of the characteristic green the vegetables to be treated are placed upon one color of a fresh unfrozen vegetable. Ordinarily, end of the belt as soon as possible after such after a frozen vegetable is thawed, it is grayish vegetables are picked or cut. Preferably such in tone and the green lacks the depth and brilvegetables first are subjected to a washing opliance of a fresh vegetable. Instead, the thawed eration with clear water. It has been found devegetable is a dirty gray-green in color. sirable to jet the water upon the vegetables, The method described hereafter permits very thereby utilizing the forcible action of the Jets large quantities of vegetables to be rapidly and in the removal of adherent dirt and foreign matproperly treated prior to freezing and results in a ter. Water at a temperature of between about setting or fixation of the original deep brilliance 90 F. and 110 F. is preferably used. water withand characteristic green color of the fresh vegein this temperature range apparently facilitattable. ing and expediting the subsequent operations. Generally stated, the method of the present in- When a temperature of about 110 F. is used at vention contemplates a. process in which the this stage. the washing period consumes about vegetables are washed, subjected to the action of 25 to 85 seconds. This time may also include a a concentrated salt solution and then blanched. short period of travel of vegetables through a Conditions of temperature, time, salt concentrazone in which draining is permitted to take tion, etc., are of importance in the rapid handling place.

of vegetables in accordance with this process on a go The belt then moves the vegetables beneath a commercial scale and the description given hereseries of nozzles supplied with an aqueous salt inafter pr these ary conditions and solution. A rather concentrated salt solution is instructions. preferably employed, that is, the aqueous solu- An object of the invention. therefore, is to distion may contain from about 20% to as high as close and provide a process of preparing fresh 3 of salt (NaCl) by weight when the concengreen vegetables for freezing whereby the tration is determined at say F. Although this natural, inherent, green coloration is fixed or set aqueous salt solution may be used at atmospheric so that after freezing and upon subsequent thawtemperatures of say 60 F. or F., it is desirable ing, the fruit or vegetable retains its natural deep to use the solution at temperatures of between green color. 0 about F. and 130 F. since a shorter treat- A further object of the invention is to dising time will sumce when the salt spray is at close and provide a process whereby large quanthese more elevated temperatures. In actual titles of vegetables may be rapidly and practipractice, a time of about 40 to 42 seconds is sufilcally continuously prepared for subsequent freezcient when the salt solution is at F.; 25 ing. the process setting or fixing the natural color 45 seconds is sufiicient when the salt solution is at of the vegetables and stoppingv oxidation, F.; as long as 60 seconds may be required enzymatic action, spoilage and the like. when the solution is at about 100 F.

These and other objects of the invention will It is to be understood that since the vegetables become apparent to those skilled in the art from are carried upon a foraminous belt or carrier, the following description in which exemplary 50 the salt solution drains quickly. Wire baskets or conditions of time, temperature, concentration, other. means may be used. Thevegetables should etc., are set forth. not be permitted to stand submerged in a con- Although the process is capable of being used centrated salt solution for any appreciable length on various vegetables, it is particularly directed of time. The salt solution spray should impinge to fresh green vegetables such as string beans, 55 the vegetables in a rather forcible manner and 3 act as a forcible rinse. Fish-tail nozzles have been found satisfactory.

By employing the concentrations, temperatures and times described hereinabove for the salt solution spray operation, the coloring is fixed or set and in many instances appears to deepen. It may also be noted that salt solutions of higher concentrations appear to produce better results on tougher vegetables whereas solutions having a concentration within the lower portion or the range indicated are preferably used on tender vegetables, The same sp ies of vegetable may be quite tender during one portion of the season and tough during another portion of the season. Vegetables from diflerent areas or those raised under different climatic or soil conditions may also vary in tenderness, so that the operator should take these variables into consideration in selecting the optimum temperature time and salt content conditions for the performance of this step oftheprocess. I

The conveyor belt may then pass through an inspection zone in which damaged or unsatisfactory vegetables are removed. Simultaneously, any excess solution drains away from the vegetables during this period of travel. Thereafter the vegetables pass into a blanching zone in which they are blanched and rapidly cooled. Blanching operations are well known and are designed to prevent spoilage by inhibiting oxidation and stopping enzymatic action, In the performance of the present process it has been found highly desirable to blanch the vegetables by 'sub- Jecting them to the action of steam so as to raise the temperature of the vegetables to about 190- 210 F. within a period of less than 5 minutes. A longer period of time appears to exert partial cooking action. Blanching at about 210 F. may be accomplished in from about 3 minutes to 3 minutes and 20 seconds, steam being introduced into the enclosure through which the belt is traveling both from points above the belt and points below the belt, so that the vegetables rapidly reach the desired blanching temperature. The blanched vegetables immediate y pass into a cooling zone in which they are sprayed with chilled water. Quick cooling is highly desirable so as to prevent slow cooking by reason of internal heat. By spraying the vegetables with water at a temperature of about 40 F., the cooling is rapidly attained and the vegetables are discharged at a temperature of about 58 F. or 60 Vegetables thus treated then go to packing tables, are packed in suitable cartons or boxes, and are then frozen.

The aqueous salt solution used for setting or fixing the color and for deepening the color may be recirculated and reused. If the vegetables have been thoroughly washed before being sub- Jected to the action of the aqueous salt solution, the solution need not be clarified or filtered very often. In some instances the preliminary washing operation may be dispensed with altogether but in that case the salt solution needs be filtered or otherwise clarified before being reused and in most instances a longer treating time is necessary. It appears that the preliminary step of subjecting the fresh green vegetables to the action of a forcible spray of water at 90-1l0 F. opens the pores or surface cells sufficiently to render the subsequent spraying with aqueous salt solution much more effective and rapid.

It will be evident to those skilled-in the art that the process described hereinabove is extremely simple and is capable of being used in handling tremendous quantities of vegetables in an emcient and economical manner. The color of frozen vegetables which have been pretreated in accordance with this process is markedly and surprisingly etter than other forms of pretreatment known heretofore.

I claim:

1. In a process of preparing fresh green vegetables for freezing, the steps of: subjecting fresh green vegetables to the action of a forcible spray of an aqueous salt solution at a temperature of between about 100 F. and 130 F. for a period of from about 25 seconds to 60 seconds, said solution having a sodium chloride content of between about 20% and 30% by weight at F., while permitting excess solution to drain from the vegetables, and then subjecting the wet vegetables to the action of steam to raise the temperature thereof to about 190 F.210 F. within a period of less than 5 minutes, and then rapidly cooling the vegetables to inhibit cooking of the vegetables.

2. A process of preparing fresh green vegetables for freezing comprising: washing fresh green vegetables with water at a temperature of between about F, and 110 F., then subjecting the washed vegetables to the action of a forcible spray of an aqueous solution having a content of between about 20% and 30% of sodium chloride at 60 F. for a period of from about 25 secends to 60 seconds, while permitting excess solution to drain therefrom, and then blanching and rapidly cooling the vegetables.

3. A process of preparing fresh green vegetables for freezing comprising: washin fresh green vegetables with water at a temperature of between about 90 F. and 110 F., then subjecting the washed vegetables tov the action of a forcible spray of an aqueous solution having a content of between about 20% and 30% of sodium chloride at 60 F. for a period of from about 25 seconds to 60 seconds, while permitting excess solution to drain therefrom, then blanching the vegetables by subjecting them to theaction of steam to raise the temperature thereof to about 190 F.- 210 F. within a period of 2 to 4 minutes, and then rapidly cooling the blanched vegetables by means of a cold water spray.

4. In a process of preparing fresh green vegetables for freezing, the step of: subjecting fresh green vegetables, prior to blanching to the action of a forcible spray of an aqueous salt solution .-at a temperature of between about F. and

130 F. for a period of from about 25 seconds to 60 seconds, said solution having a sodium chloride content of between about 20% and 30% by weight at 60 F., while permitting excess solution to drain from the vegetables.

5. In a process of preparing fresh green vegetables for freezing, the steps of: washing fresh green vegetables with clear water, and then sub- Jecting the washed vegetables to the action of a spray of aqueous solution containing between about 20% and 30% by weight of sodium chloride (at 60 F.), while permitting excess solution to drain from the vegetables, for a length of time sufficient to set the color of the vegetables and retard the development of a grayish, lack-luster appearance in the vegetables upon subsequent freezing and thawing.

6. In a process of preparing fresh green vegetables for freezing, the steps of: washing fresh green vegetables with clear water at a temperature of between about 90 F. and F., and then subjecting the washed vegetables to the ac- REFERENCES CITED The following references are of record in the file of this patent:

Tressler et 9.1., Freezing Preservation 01' Foods, Avl. Pub. Co., 1943, N. Y. 0., pp. 380-381. 

